A simple strategy for the analysis of the cycle-to-cycle variation of premixed combustion process in ICEs

In car engines, combustion often occurs in the wrinkled laminar or flamelet regime: the flame thickness is smaller than the smallest vortex size and the turbulent intensity is of the same order as the laminar flame velocity. In this paper, we compare a very inexpensive numerical approach for two-dimensional (1D cylindrical or 2D planar) fronts to experimental results. The front is considered as an active infinitely thin interface, separating fresh and burnt gases. Its evolution is modeled thanks to a Michelson-Sivashinsky type of equation, that includes non linear Huy-gens normal propagation, curvature effects and hydrodynamic (Landau-Darrieus) instability. Turbulence influence is taken into account as a collection of vortices, generated via an ad hoc procedure, and which velocity fields have beforehand been modified to mimic the thermal dilatation of the expanding gas. Numerical simulations, in the cylindrical case, are then compared to experimental results. The relative increase of flame speed - equal to the relative increase of flame surface area [1] - and front shapes can then be compared for different turbulence intensities. The strategy gives also access to overall combustion times distributions.